The object of the present invention is a process for removing fluorinated impurities from olefins.
The French Pat. No. 2,443,877 discloses an improved catalytic composition and its use as oligomerization catalyst for monoolefins, for example those having from 2 to 4 carbon atoms, and particularly as dimerization and/or trimerization catalyst therefor. This catalytic composition consists of the product obtained by contacting, in any order, a bivalent nickel compound with a hydrocarbyl aluminum halide and an organic Bronsted acid. The best results are obtained with the use, as Bronsted acid, of a halogenocarboxylic acid, for example trichloracetic acid or trifluoracetic acid. However an additional problem has appeared: all or part of the halogen is found in the resultant olefinic oligomerizate, which is unacceptable for a number of uses of this oligomerizate. The difficulty to remove the traces of halogen was then encountered. In view of the acidic nature of the halogenated compounds introduced into the catalyst, it could be expected that washing the oligomerizate with water or with an inorganic base such as sodium hydroxide, potassium hydroxide or ammonia in aqueous medium would remove these traces of halogen. The failure of this method shows that the halogen is no longer in the form of a halogenocarboxylic acid, that the problem has no obvious solution and that the halogen is probably found in the form of a compound soluble in hydrocarbons and which cannot be extracted easily.